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JavaScript JavaScript Array Iteration Methods Array Manipulation Practice reduce()

Joe Mbome
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Joe Mbome
Front End Web Development Techdegree Graduate 17,249 Points

phoneNumbers is array of 10 digit phone numbers, where the first three digits, in parentheses, are area codes. Using red

not sure how to go about this

app.js
const phoneNumbers = ["(503) 123-4567", "(646) 123-4567", "(503) 987-6543", "(503) 234-5678", "(212) 123-4567", "(416) 123-4567"];
let numberOf503;

// numberOf503 should be: 3
// Write your code below
numberOf503= phoneNumbers.reduce((acc,number)=>number.substr(0,2)===503, 0);

1 Answer

Blake Larson
Blake Larson
12,946 Points

The substring function will return a string so you want to compare it to "503". substring(1, 4) gets the 3 numbers between the parentheses. Pretty sure this will pass this challenge.

numberOf503 = phoneNumbers.reduce((acc, number) => {
  if(number.substring(1, 4) === "503") {
    acc++
  }
  return acc;
} , 0);

I would definitely use filter for something like this though when you get to use what you want. Just easier to use and cleaner. That would be like this in future scenarios.

numberOf503 = phoneNumbers.filter((number) => number.substring(1, 4) === "503").length;